In terms of price, I'd say MAC is one of the best. Mine fits like a glove, and was $100 less than it's nearest competitor. Nicely engineered with good quality polished metal.
For performance, you may pick up 3-4 HP. They usually say around 5% for an intake, 5% for exhaust. You will notice the engine revs faster, with good high end accelaration. Don't expect to be blown from your seat.